On Sat, Jul 11, 2020 at 02:13:46AM -0700, Ram Pai wrote:
> The page requested for page-in; sometimes, can have transient
> references, and hence cannot migrate immediately. Retry a few times
> before returning error.
As I noted in the previous patch, we need to understand what are these
transient errors and they occur on what type of pages?
The previous patch also introduced a bit of retry logic in the
page-in path. Can you consolidate the retry logic into a separate
patch?
>
> H_SVM_PAGE_IN interface is enhanced to return H_BUSY if the page is
> not in a migratable state.
>
> Cc: Paul Mackerras <pau...@ozlabs.org>
> Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org>
> Cc: Michael Ellerman <m...@ellerman.id.au>
> Cc: Bharata B Rao <bhar...@linux.ibm.com>
> Cc: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
> Cc: Sukadev Bhattiprolu <suka...@linux.vnet.ibm.com>
> Cc: Laurent Dufour <lduf...@linux.ibm.com>
> Cc: Thiago Jung Bauermann <bauer...@linux.ibm.com>
> Cc: David Gibson <da...@gibson.dropbear.id.au>
> Cc: Claudio Carvalho <cclau...@linux.ibm.com>
> Cc: kvm-...@vger.kernel.org
> Cc: linuxppc-dev@lists.ozlabs.org
>
> Signed-off-by: Ram Pai <linux...@us.ibm.com>
> ---
> Documentation/powerpc/ultravisor.rst | 1 +
> arch/powerpc/kvm/book3s_hv_uvmem.c | 54
> +++++++++++++++++++++---------------
> 2 files changed, 33 insertions(+), 22 deletions(-)
>
> diff --git a/Documentation/powerpc/ultravisor.rst
> b/Documentation/powerpc/ultravisor.rst
> index d98fc85..638d1a7 100644
> --- a/Documentation/powerpc/ultravisor.rst
> +++ b/Documentation/powerpc/ultravisor.rst
> @@ -1034,6 +1034,7 @@ Return values
> * H_PARAMETER if ``guest_pa`` is invalid.
> * H_P2 if ``flags`` is invalid.
> * H_P3 if ``order`` of page is invalid.
> + * H_BUSY if ``page`` is not in a state to pagein
>
> Description
> ~~~~~~~~~~~
> diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c
> b/arch/powerpc/kvm/book3s_hv_uvmem.c
> index 12ed52a..c9bdef6 100644
> --- a/arch/powerpc/kvm/book3s_hv_uvmem.c
> +++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
> @@ -843,7 +843,7 @@ unsigned long kvmppc_h_svm_page_in(struct kvm *kvm,
> unsigned long gpa,
> struct vm_area_struct *vma;
> int srcu_idx;
> unsigned long gfn = gpa >> page_shift;
> - int ret;
> + int ret, repeat_count = REPEAT_COUNT;
>
> if (!(kvm->arch.secure_guest & KVMPPC_SECURE_INIT_START))
> return H_UNSUPPORTED;
> @@ -857,34 +857,44 @@ unsigned long kvmppc_h_svm_page_in(struct kvm *kvm,
> unsigned long gpa,
> if (flags & H_PAGE_IN_SHARED)
> return kvmppc_share_page(kvm, gpa, page_shift);
>
> - ret = H_PARAMETER;
> srcu_idx = srcu_read_lock(&kvm->srcu);
> - down_write(&kvm->mm->mmap_sem);
>
> - start = gfn_to_hva(kvm, gfn);
> - if (kvm_is_error_hva(start))
> - goto out;
> -
> - mutex_lock(&kvm->arch.uvmem_lock);
> /* Fail the page-in request of an already paged-in page */
> - if (kvmppc_gfn_is_uvmem_pfn(gfn, kvm, NULL))
> - goto out_unlock;
> + mutex_lock(&kvm->arch.uvmem_lock);
> + ret = kvmppc_gfn_is_uvmem_pfn(gfn, kvm, NULL);
> + mutex_unlock(&kvm->arch.uvmem_lock);
> + if (ret) {
> + srcu_read_unlock(&kvm->srcu, srcu_idx);
> + return H_PARAMETER;
> + }
>
> - end = start + (1UL << page_shift);
> - vma = find_vma_intersection(kvm->mm, start, end);
> - if (!vma || vma->vm_start > start || vma->vm_end < end)
> - goto out_unlock;
> + do {
> + ret = H_PARAMETER;
> + down_write(&kvm->mm->mmap_sem);
Again with ksm_madvise() moved to init time, check if you still need
write mmap_sem here.
Regards,
Bharata.
